Effects of tissue-type plasminogen activator (t-PA) on Streptococcus sanguis-infected endocardial vegetations in vitro.

The effects were studied of in-vitro exposure to tissue-type plasminogen activator (t-PA) on endocardial vegetations isolated from rabbits with Streptococcus sanguis endocarditis as well as on Str. sanguis-infected plasma clots. For both vegetations and clots t-PA induced lysis of the infected fibrin matrix, demonstrated by a release of streptococci into the incubation medium and by an increase in the concentration of fibrin degradation products. The clots decreased in weight, whereas only partial lysis of the vegetations was obtained. Addition of plasminogen to the incubation medium did not enhance the effect of t-PA on vegetations. Fibrinolysis by t-PA did not interfere with the antimicrobial action of benzylpenicillin on the bacteria in a fibrin matrix. It is concluded that t-PA can degrade the fibrin matrices of infected endocardial vegetations and plasma clots. Reduction of vegetation size by t-PA may prove to be useful in the treatment of bacterial endocarditis.